Dipole antenna with combination feed-support rods



LBW) mlr Lnmwma Aug. 8', 1967 R. M. SILLIMAN DIPOLE ANTENNA WITH COMBINATION FEED-SUPPORT RODS Filed March 31, 1964 2 Sheets-Sheet l Z6? 54 3 J6 (472 W .z ,4 972 INVENTOR E522?)- Mflzu/mw BY i v ATTORNEYS 1967 R. M. SILLIMAN 3,335,420

DIPOLE ANTENNA WITH COMBINATION FEED-SUPPORT RODS Filed March 31, 1964 2 Sheets-Sheet 2 #4 F m I a 42;

INVENTOR jFaaief f .5741010 BY Z ATTORNEYS United States Patent ice 3,335,420 DIPOLE ANTENNA WITH COMBINATION FEED-SUPPORT RODS Robert I. Silliman, Silver Spring, Md., assignor to Electronics Research, Inc. of Evansville, Evansville, Ind., a corporation of Indiana Filed Mar. 31, 1964, Ser. No. 356,296 13 Claims." (Cl. 343-793) This invention relates to antenna systems, and particularly to dipole type antennas for use in any desired frequency range, for example in the television and FM frequency ranges. More particularly, the invention relates to a fully closed antenna for vertical polarization. As a specific example of its use, it may be employed to add vertical polarization to an FM antenna. It may be used in combination with any type of horizontally polarized FM antenna which substantially matches or can be substantially matched to its feed line. The antenna may also be employed in any number of bays up to ten or more. The free space horizontal radiation pattern of this antenna is circular within :1 db, and its power gain is the same as that of a half wave dipole antenna.

In construction, the antenna includes a support or mast section which externally has a metal tube inside of which is a rigid coaxial feed line. This coaxial feeder itself has a rigid outer section and an inner rod. Perpendicular to the mast section are two arm sections, center fed. Each arm section includes a hollow metal radiating or receiving cylinder closed at its outer end and open at its inner end. These metal cylinders are each somewhat shorter than a quarter wave length, and each is connected at its inner end internally by electrical connection means including respective rod means that otherwise connect to the coaxial outer section and inner rod. Surrounding the rod means and extending from the metal tube of the mast section, as a part of the arm sections, are electrical insulating means, such as dielectric sleeves, for insulatively supporting the hollow metal cylinders of the arm sections. These sleeves are securely connected between that metal tube and the inner ends of those cylinders. This provides for a fully closed antenna in which any desired gas such as dried nitrogen or dried air under pressure may be utilized. Between the outer conductor of the coaxial feed line and the surrounding metal tube there is preferably employed a metal slug for tuning purposes so as to prevent interference with horizontal polarization by other horizontally polarized antennas, if any is employed with the antenna of this invention.

It is therefore an object of this invention to provide an improved dipole antenna construction embodied as above indicated and having the advantages and characteristics mentioned herein. Other objects and advantages of this application will become apparent to those of ordinary skill in the art upon reading the appended claims in conjunction with the following detailed disclosure and drawings, in which:

FIGURE 1 illustrates one embodiment of the invention, partially in cross section;

FIGURE 2 is a cross sectional view taken substantially along the line 2-2 of FIGURE 1;

FIGURE 3 is a cross sectional view taken substantially along the line 3-3 of FIGURE 1;

FIGURE 4 is a cross sectional view taken substantially along the line 4-4 of FIGURE 1;

FIGURE 5 illustrates a partial cross sectional view of another embodiment;

FIGURES 6 and 7 are cross sectional views taken substantially along the lines 6--6 and 77 of FIGURE 5, respectively; and

3,335,420 Patented Aug. 8, 1967 FIGURE 8 is still another partial cross sectional View of an embodiment of the invention.

While the antenna may be employed for either reception or transmission purposes, and may be used in any desired range of frequencies, the dimensions set forth below in this detailed specification for exemplary purposes, are related to the present FM band of frequencies, 88-108 mc. Of course, it can be used in the higher and/ or lower television frequency bands, as desired, including channels 2 through 83, as well as any other broadcast, communication, radar, etc., range of frequencies.

The support or mast section 10 for the antenna of FIGURE 1 includes an outer rigid metal tube having an outer diameter of 3.125 inches, for example. At its lower end, this tube is secured, as by welding, to a base plate 14, which in turn is secured by any desired means such as bolts 16 to a metal housing or mounting block 18 in which is terminated a coaxial feed line 20. By virtue of the inner coaxial conductor 22 extending in opposite directions with elements 24, a connection may be made to either or both sides of the mounting block, by a conventional coaxial transmission line, whereby several of such antennas as the one being described, can be electrically interconnected in any manner desired.

At the upper end of the mast section 10, the outer metal tube 12 is connected in any desirable manner to a tube section 26 which extends in opposite directions perpendicular to tube 12. This tube or cylinder 26 is part of the two arm sections 28 and 30 of the dipole antenna. Further included in arm section 28 is a cylindrical radiating member or tube 32, which has its outer ends closed by cap 34 and its inner end 36 open so as to communicate internally with cylinder 26, by way of an insulator 38, which is in the form of a dielectric sleeve. Preferably, this sleeve provides the main support of cylinder 32 and is secured on the inner side of cylinders 26 and 32 by means of O-rings 40 of rubber or the like. These rings fit in a groove in the plastic sleeve 38, with the tubing or cylinders 26 and 32 fitting over the O-rings.

Arm section 30 is constructed similar to the other arm section 38, and includes a radiating cylindrical tube 42 closed by end cap 44 and supported by a plastic sleeve 46, which is secured to cylinders 26 and 42 by O-rings 40 as described above for arm section 28.

In order to connect the radiator elements 32 and 42 to the coaxial feed line 20, the inner rigid rod 22 thereof is adapted with a threaded element 48 which, in turn, is screwed into a rod 50. This rod extends in both directions, the full length of both arm sections, in this embodiment, to help support the radiation cylinders 32 and 42, the outer ends of the rod being secured to the end caps as by bolts 52 and 54. It is not this outer end connection to the radiator elements, however, that is utilized to feed these elements with the currents from the transmisison line. Instead, a disk or metal slug 56 is positioned inside radiator element 32 adjacent its inner end 36 for receiving rod 50. The rod passes through an aperture in the disk, but is electrically secured, as by bonding, to the disk, which in turn is bonded or otherwise electrically secured internally to the radiator 32. In effect, then, the remaining portion of rod between disk 56 and end cap 34 serves no electrical connection function but aids in mechanical supporting radiator 32. The same is true for the portion of rod 50 which extends from the center connector 48 to the outer end of radiator 42, which is electrically fed in the manner now described.

The outer rigid coaxial conductor 58 of the feed line 20 extends above the upper end of the inner coaxial rod 22, and contains opposite apertures 60 through which rod 50 extends. At it suppermost portion, the outer coaxial conductor 58 has rods 62 and 64 secured to it, on opposite sides. These may be bolted to conductor 58 as shown, and they extend to end caps 34 and 44, to which they are secured as by respective bolts 66 and 68. Again, the radiating elements 32 and 42 are not electrically fed by these outer end connections to rods 62 and 64. Instead, at its inner end 70, radiator element 42 has internally secured to it a metal disk or slug 72, which is similar to disk 56. Rod 62 passes through an aperture in disk 72, and is electrically connected thereto, as by bonding, whereby the outer coaxial feed conductor 58 electrically connects via rod 62 to the inner end 70 of radiator element 42. The remaining portion of rod 62, between disk 72 and the outer end of radiator 42, aids some in a mechanical sense but has no electrical connection function. The same is true for rod 64, since it is not electrically connected to disk 56 but passes therethrough by way of an aperture 74, which as shown in FIGURE 2. is larger in diameter than rod 64. Rod 50 clears an aperture in disk 72, in the same manner.

As above indicated, the outer tube 12 of the mast section may be 3.125 inches in diameter, and the same dimension maybe applied to cylinders 26, 32 and 42, all of which are preferably of copper. Coaxial feed conductor 58 is smaller, of course, for example 2% inch diameter or less. It too is preferably a copper pipe. The length of the mast section may be 36 inches, while the total length of the dipole arm sections from end cap to end cap is approximately 45 inches. Plastic sleeves 38 and 46 can be approximately 2% inches each in length, by one-half inch thick. Since cylinder 26 extends perpendicularly from the outer mast tube 12 only a small amount, such as one inch, this means radiator elements 32 and 42 are each about 19 inches. With these dimensions representing a design for an FM antenna, the center frequency of which is 98 mc., it is apparent the overall length of the arm sections of 45 inches is substantially less than the half wave length on approximately 60 inches, and that the radiator elements 32 and 42 are each considerably less than a quarter wave length. That is, the physical dimensions of the arm sections do not correspond to those wave length dimensions, but on the other hand the apparent electrical effect of the antenna corresponds to that of a half wave length dipole antenna.

As above indicated, this antenna may be filled with any desired type of gas. Since the mast section and arm sections 28 and 30 are fully closed and communicate with one another, with all joints and the like being sealed, there is a closed volume in which gas may be introduced.

It has been indicated also that this vertically polarizing antenna may be employed in conjunction with one or more horizontally polarizing antennas, and that under such circumstances it is preferable to suppress any horizontal polarization that the antenna of FIGURE 1 might supply when the mast section thereof is disposed horizontally for effecting vertical polarization by the dipole arm sections. Accordingly, a tuning or choke slug 76 is initially driven into correct longitudinal positon between the metal tube 12 and the outer coaxial conductor 58 before mounting block 18 and plate 14 are attacked, in order to pre-tune out undesired polarization effects which mast section 10 might otherwise produce at the operating frequency.

It will be appreciated that the center coaxial conductor 22 may be replaced by a different center conductor to effect a different matching impedance, as required for whatever type of insulation is at hand.

While it has above been indicated that the extra length of rods 50, 62 and 64 in FIGURE 1 are in eiTect electrically absent, this is to say that they are not essential electrically, though they might affect the band width of the antenna. An embodiment of this invention, which does not have these extra lengths of such rods is shown in FIGURE 5. Radiating cylinders 32' and 42' are substantially the same as the corresponding radiator elements in FIGURE 1, except that end caps 34' and 44' do not have mechanical connections to any internal rods, but do externally conect to electrical connectors 56 and 72 by way of screws 78, for example. These electrical connectors are disposed adjacent the inner open ends of the radiating cylinders and are electrically connected to rods 50 and 62' respectively, which in turn connect to the inner coaxial rod 22 and the outer coaxial conductor 58'. As previously indicated, plastic sleeves 38 and 46 in the embodiment of FIGURE 1 are the main supports for the cylindrical radiators 32 and 42. In the FIGURE 5 embodiment, these sleeves are substantially the full support therefor, rods 50' and 62' being of little aid in this respect, but mainly operating mechanically to hold the coaxial conductors 22 and 58' in their proper relative positions. Otherwise, the antenna in FIGURE 5 operates in the same manner as that in FIGURE 1.

A still different version of this invention is set forth in FIGURE 8. In this case, rods 50 and 62" extend through the respective electrical connection elements 56" and 72", being electrically secured thereto as by bonding so as to feed the radiating tubes 32" and 42" adjacent their respective inner ends. Each of the rods 50 and 62" further extend to and are secured to end caps 34" and 44" to add some mechanical strength. Except for the difference in mechanical structural aid, the antenna of FIG- URE 8 operates electrically substantially the same as those in FIGURES 1 and 5.

From the foregoing, it is apparent that this invention has provided structure which accomplishes all of the objects and has all of the advantages herein mentioned. Still other objects and advantages, and even further modifications of the invention, will become apparent to those of ordinary skill in the art upon reading this disclosure.

However, it is intended that this disclosure be considered exemplary, and not limitative, the scope of the invention being defined by the appended claims.

What is claimed is:

1. A fully closed dipole antenna comprising:

a mast section including an outer metal tube and an inner rigid coaxial feed line having a rigid outer section and an inner rod, and

two substantially equal arm sections extending in a straight line in opposite directions from and at right angles to said mast section,

each said arm section including a hollow metal cylinder closed at its outer end and open at its inner end,

electrical connection means including first and second rod means for rigidly interconnecting said inner cylinder ends respectively to said coaxial outer section and inner rod, and

electrical insulating means extending from said metal tube as part of said arm sections and surrounding said rod means for insulatively supporting said cylinders, at the aforesaid right angles relative to said metal tube, by secured connection to said cylinder inner ends.

2. An antenna as in claim 1 wherein said arm sections include a third hollow cylinder both ends of which are open and which connects at its center to said outer metal tube of the mast section, said electrical insulating means being two sleeve-like insulators respectively coupling the said third cylinder outer ends to the said inner ends of said closed cylinders.

3. An antenna as in claim 1 wherein said first and second rod means are respective rods extending the full length of their respective arm section and connecting to the said closed outer end thereof.

4. A fully closed dipole antenna for transmitting signals with vertical polarization in a desired frequency range in at least the television and FM bands, comprising:

a mast section including a first hollow outer metal tube and therein an inner rigid coaxial feed line having a rigid outer section and an inner rod,

a second hollow metal tube open at both ends and extending perpendicular to said mast slightly beyond the edges of and connectably centered on said outer metal tube for interior communication therewith,

said coaxial feed line extending into the hollow interior of said second tube,

first and second hollow metal cylinders closed at their outer ends and open at their inner ends,

two insulating sleeves respectively connecting the said inner ends of said cylinders to the opposite ends of said second tube for supporting said cylinders, and

electrical connection means comprising first and second rod means for rigidly interconnecting the said cylinder inner ends to the said coaxial outer section and inner rod respectively at the portion of said feed line which extends as aforesaid into the interior of said second tube.

5. An antenna as in claim 4 wherein the distance between the closed ends of said first and second cylinders are substantially a half wave length electrically speaking as to a given frequency in said desired range, but is substantially less than a half wave length physically speaking for that frequency, said cylinders being each considerably less in physical length than a quarter wave length for that frequency.

6. An antenna as in claim 12 and further including pressurized gas filling the intercommunicating hollow tubes and cylinders including said outer metal tube to the position of said choke.

7. An antenna as in claim 4 wherein said electrical connection means comprises two rods respectively connecting the said outer section and inner rod of said coaxial feed line to the inner ends of said first and second cylinders.

8. An antenna as in claim 7 wherein said rods extend from the said inner ends of the first and second cylinders onto the closed ends thereof for securement thereto to aid mechanical strength and support for said first and second cylinders.

. A fully closed dipole antenna comprising:

a mast section including an outer metal tube and an inner rigid coaxial feed line having a rigid outer section and an inner rod, and

two substantially equal arm sections extending in a straight line in opposite directions from and at right angles to said mast section,

each said arm section including a hollow metal cylinder closed at its outer end and open at its inner end,

electrical connection means including first and second rod means for internally connecting said inner cylinder ends respectively to said coaxial outer section and inner rod, two rod-like connectors respectively at the said inner ends of said cylinders, said rod means being two arm rods extending respectively from said coaxial outer section and inner rod only to, said rod connectors,

electrical insulating means extending from said metal tube as part of said arm section-s and surrounding said rod means for insulatively supporting said cylinders, at the aforesaid right angles relative to said metal tube, by secured connection to said cylinder inner ends.

10. A fully closed dipole antenna comprising:

a mast section including an outer metal tube and an inner rigid coaxial feed line having a rigid outer section and an inner rod, and

two substantially equal arm sections extending in a straight line in opposite directions from and at right angles to said mast section,

each said arm section including a hollow metal cylinder closed at its outer end and open at its inner end,

electrical connection means including first and second rod means for internally connecting said inner cylinder ends respectively to said coaxial outer section and inner rod, each of said rod means extending the full length of both said arm sections and connecting at both its ends to the closed ends of said cylinders,

electrical insulating mean-s extending from said metal tube as part of said arm sections and surrounding said rod means for insulatively supporting said cylinders, at the aforesaid right angles relative to said metal tube, by secured connection to said cylinder inner ends.

11. A fully closed dipole antenna comprising:

a mast section including an outer metal tube, an inner rigid coaxial feed line having a rigid outer section and an inner rod, and means for preventing effective radiation from said mast section in a polarization perpendicular to the polarization effected by said arm sections,

two substantially equal arm sections extending in a straight line in opposite directions from and at right angles to said mast section,

each said arm section including a hollow metal cylinder closed at its outer end and open at its inner end,

electrical connection means including first and second rod means for internally connecting said inner cylinder ends respectively to said coaxial outer section and inner rod, and

electrical insulating means extending from said metal tube as part of said arm sections and surrounding said rod means for insulatively supporting said cylinders, at the aforesaid right angles relative to said metal tube, by secured connection to said cylinder inner ends.

12. A fully closed dipole antenna for transmitting signals with vertical polarization in a desired frequency range in at least the television and FM bands, comprising:

a mast section including a first hollow outer metal tube and therein an inner rigid coaxial feed line having a rigid outer section and an inner rod,

a choke in said mast section between said rigid outer tube and outer coaxial section for tuning the mast section to prevent horizontal polarization interference,

a second hollow metal tube open at both ends and extending perpendicular to said mast slightly beyond the edges of and connectably centered on said outer metal tube for interior communication therewith,

said coaxial feed line extending into the hollow interior of said second tube,

first and second hollow metal cylinders closed at their outer ends and open at their inner ends,

two insulating sleeves respectively connecting the said inner ends of said cylinders to the opposite ends of said second tube for supporting said cylinders,

electrical connection means for rigidly interconnecting the said cylinder inner ends to the said coaxial outer section and inner rod respectively at the portion of said feed line which extends as aforesaid into the interior of said second tube.

13. A fully closed dipole antenna for transmitting signals with vertical polarization in a desired frequency range in at least the television and FM bands, comprising:

a mast section including a first hollow outer metal tube and therein an inner rigid coaxial feed line having a rigid outer section and an inner rod,

21 second hollow metal tube open at both ends and extending perpindicular to said mast slightly beyond the edges of and connectably centered on said outer metal tube for interior communication therewith,

said coaxial feed line extending into the hollow interior of said second tube,

first and second hollow metal cylinders closed at their outer ends and open at their inner ends,

two insulating sleeves respectively connecting the said inner ends of said cylinders to the opposite ends of said second tube for supporting said cylinders, and

electrical connection means comprising: first and second rod means for rigidly interconnecting the said cylinder inner ends to the said ,coaxial outer section 7 and inner rod respectively at the portion of said feed line which extends as aforesaid into the interior of said second tube, said second rod means extending the full length of both said cylinders and being connected at both its ends to the closed end of said cylinders, said first rod means extending from the inner end of one of said cylinders onto the closed end thereof for securement thereto and third rod means extending in substantial alignment with said first rod means and being mechanically secured between said outer coaxial section and the closed end of the other said cylinder.

References Cited UNITED STATES PATENTS 2,199,375 4/1940 Lindenblad 343790 5 2,274,389 2/1942 Von Baeyer et al. 343791 2,451,258 10/1948 Trevor 343-79l 2,945,232 7/1960 Jasik 343-807 3,030,622 4/ 1962 Leitner et al 343-821 X HERMAN KARL SAALBACH, Primary Examiner. 10 ELI LIEBERMAN, Examiner.

R. F. COHN, Assistant Examiner. 

1. A FULLY CLOSED DIPOLE ANTENNA COMPRISING; A MAST SECTION INCLUDING AN OUTER METAL TUBE AND AN INNER RIGID COAXIAL FEED LINE HAVING A RIGID OUTER SECTION AND AN INNER ROD, AND TWO SUBSTANTIALLY EQUAL ARM SECTIONS EXTENDING IN A STRAIGHT LINE IN OPPOSITE DIRECTIONS FROM AND AT RIGHT ANGLES TO SAID MAST SECTION, EACH SAID ARM SECTION INCLUDING A HOLLOW METAL CYLINDER CLOSED AT ITS OUTER END AND OPEN AT ITS INNER END, ELECTRICAL CONNECTION MEANS INCLUDING FIRST AND SECOND ROD MEANS FOR RIGIDLY INTERCONNECTING SAID INNER CYLINDER ENDS RESPECTIVELY TO SAID COAXIAL OUTER SECTION AND INNER ROD, AND ELECTRICAL INSULATING MEANS EXTENDING FROM SAID METAL TUBE AS PART OF SAID ARM SECTIONS AND SURROUNDING SAID ROD MEANS FOR INSULATIVELY SUPPORTING SAID CYLINDERS, AT THE AFORESAID RIGHT ANGLES RELATIVE TO SAID METAL TUBE, BY SECURED CONNECTION TO SAID CYLINDER INNER ENDS. 